There are two other very popular cloud storage sites out there: Carbonite and DropBox.
I use Carbonite and I like it. At first, I had difficulties getting it to run smoothly. More specifically, it seemed to slow down my computer when it was busy storing information. But the tech support section was very helpful and we got that resolved. You get unlimited storage at Carbonite for $59 a year.
I also use Dropbox. I wrote a more detailed post on Dropbox which includes a short video on how it works. You get 2.5 gigabytes of free storage but you can access it directly on any of your computers and most smart phones. In other words, your files are in a folder on your desktop computer, in a folder in your laptop and in the cloud. You make a change to one of these files on your desktop and the updated file shows up in the cloud AND on your laptop (as long as your laptop can access the Internet).
The Amazon cloud drive seems pretty simple and straightforward. It looks like they created it initially to give people a place to store music purchases made at Amazon. But you can upload and store any kind of file there.
I have not heard any horror stories of folks having their files stolen at any of the three storage sites mentioned here.
To get started with Amazon cloud drive, click here.